In traction applications, transformers are conventionally used for galvanic decoupling and transformation of electrical power. To provide high-power conversion, transformers need to be designed with a substantial size and weight. Due to the high power involved, cooling and insulation constraints are to be considered in the transformer design.
In order to meet the requirements of traction applications, traction transformers are usually encased in oil-filled tanks having forced oil circulation and forced air cooling. Due to the restricted heat dissipation through oil, the size and weight of the above kind of transformers cannot be further reduced.
Document CN 103035370 discloses an oil-immersed transformer device including a transformer disposed in a transformer tank. The transformer is mounted in the transformer tank. The transformer tank is filled with oil. A cooling duct for cooling the oil is provided in the transformer tank, wherein water is fed through the cooling duct.
Document WO 2014/086948 A2 discloses a transformer for traction applications with windings immersed in an oil filled enclosure. The closed loop core extends through the inner of a central inner cylinder element which forms part of the enclosure and is therefore not in contact with oil.
The known solutions leave room for improvement. In view of the above, there is a need for the present invention.